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Introduction: Several studies indicate the role of mesenchymal stem cells (MSCs) as an important tool in regenerative medicine associated with injuries that affect the central nervous system (CNS). The MSCs have the capacity to differentiate into cells of the embryonal tissue, such as the mesoderm. So, these cells can be found in a variety of tissues. Also, the MSCs can release immunomodulatory and neurotrophic factors performance as inflammation mediators operating in injured tissue the regeneration. Furthermore, they can differentiate into neural, like cells in vitro. Thereby, because of the high immunomodulatory role of MSCs, this review sought to describe the main immunomodulatory mechanisms performed by MSCs in CNS recovery after tissue injury or neurodegenerative diseases. Methods: PubMed and ScienceDirect were searched between January 2011 to March 2021 and 43 articles met the criteria of the review. Results: This systematic review indicate that MSCs were used in vivo experimental Multiple Sclerosis (MS), Parkinson's disease (PA), Alzheimer's disease (AD), Amyotrophic Lateral Sclerosis (ALS), Ischemic Stroke (IS) and Traumatic Brain Injury (TBI). The treatment MSCs were usually from human origin, derived from bone marrow and administered intravenously. Discussion/Conclusion: It was shown that MSCs, independent from origin or administration pathway, can reduce inflammation and help in the recovery and preservation of injured neural tissue. Thus, the use of MSCs represents a potential therapeutic option in the treatment of neurological disorders mediated by inflammatory processes.

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In the present study, we examined the putative roles of the periaqueductal gray (PAG) in the expression of defensive responses in animals exposed to a natural predator. Previous studies have shown that predator exposure induces increased Fos expression in the dorsal part of the rostral PAG and in the ventrolateral part of the caudal PAG. According to the present findings, citotoxic NMDA lesions either in the dorsal part of the rostral PAG or in the ventrolateral part of the caudal PAG abolished freezing responses and increased risk assessment behaviors during predator exposure. In contrast, lesions combining the dorsal part of the rostral PAG and the ventrolateral part of the caudal PAG abolished both freezing and risk assessment responses. We have further investigated Fos expression in prosencephalic sites mobilized during the predator exposure, and particularly in the animals with combined lesions in both the dorsal part of the rostral PAG and the ventrolateral part of the caudal PAG, we found a significant decrease in Fos expression in the posterior part of the anterior hypothalamic nucleus (AHNp; an important target of the PAG) and in the lateral septum (which receives a dense projection from the AHNp). Importantly, the PAG lesions did not affect the mobilization of other prosencephalic sites responsive to predators. Overall, our results suggest that both the dorsal part of the rostral PAG and the ventrolateral part of the caudal PAG are critical for the expression of freezing responses. On the other hand, risk assessment behavior seems to be modulated by the PAG through a circuit involving he AHNp and the lateral septum. At this point, further studies are obviously needed to investigate whether the lateral septum is a critical site for expression of risk assessment responses.